1. Field of the Invention
This invention belongs to the field of pharmaceutical chemistry, and provides an advantageous process for preparing a group of 6-hydroxy-2-(4-hydroxyphenyl)-3-[4-(2-aminoethoxy)benzoyl]benzo[b]thiophen es. The process uses methyl groups to protect the hydroxy groups during the synthesis, and provides the compounds in excellent yield without isolating the intermediate product.
2. State of the Art
U.S. Pat. No. 4,133,814, of Jones and Suarez, first taught most of the compounds which are prepared by the process of this invention, and showed a number of processes for preparing them. The patent shows the use of phenacyl, halophenacyl and alkyl protecting groups. The process does not, however, suggest the particularly advantageous way to use a methyl protecting group which is provided by this invention.
Fujita et al. have shown the use of aluminum halide-thiols as a reagent for the demethylation of various aliphatic and aromatic ethers. The compounds on which they worked, however, were of a very stable nature, and it is believed that Fujita's work suggests that aluminum halide-thiol could not be applied to the complex polyfunctional molecules with which this invention is concerned. Fujita's work was published in Chemistry Letters, 97-98 (1979), Tet. Let., 5211-14 (1978), and J. Org. Chem. 45, 4275-77 (1980).